Control system of generator for a vehicle

ABSTRACT

A system for controlling a vehicular generator, includes: a voltage controlling device  1  for adjusting a generator output voltage a generator  10  connected to an in-vehicle battery  4  to a predetermined voltage, the voltage controlling device  1  including external voltage sensing terminal S for detecting an external voltage of the generator  10 , and the generator output voltage being adjusted through on/off control of a field current of the generator  10  in accordance with the external voltage, in which an external control unit  5  is inserted between the external voltage sensing terminal S and the battery  4  to cause a voltage drop. Consequently, it is possible to dispense with an exclusive input terminal for external signal, thereby enabling simple system configuration cost reduction.

TECHNICAL FIELD

The present invention relates to a system for controlling a vehicular ACgenerator provided with a voltage controlling device having an externalvoltage sensing terminal, and more particularly to a system forcontrolling a vehicular generator which requires no exclusive inputterminal for an external signal, thereby simplifying systemconfiguration and achieving cost reduction.

BACKGROUND ART

In general, a system for controlling a vehiclular generator includes avoltage controlling device having an external voltage sensing terminal.When a key switch of a vehicle is closed, a power transistor is madeconductive by flowing of a base current, resulting in a field currentflowing through a field coil, thereby enabling an AC generator (referredto as simply “generator” hereinafter) to output a generator voltage.Further, a constant-voltage power supply is produced from a batteryvoltage and a reference voltage is generated by the constant-voltagepower source.

When the generator starts to generate electric power due to starting ofan in-vehicle engine, the voltage controlling device operates so thatthe battery voltage to be detected by the external voltage sensingterminal exceeds the reference voltage to make a transistor 103conductive and to turn off a power transistor 101, whereby the fieldcurrent reduces and the generator output voltage of the generatorlowers. In addition, when the battery voltage becomes lower, the powertransistor is made conductive, and therefore the field current increasesto raise the generator output voltage of the generator.

Furthermore, for example, Japanese Pat. No. 3102981 discloses atechnology that an adjustment voltage varies in accordance with a dutysignal from an external control unit related to a voltage controllingdevice.

DISCLOSURE OF THE INVENTION

Since a conventional system for controlling a vehiclular generator isconfigured as described above, there arises a problem in that anexclusive input terminal for an external signal needs to be provided ina voltage controlling device, thereby increasing the number of wiringsfor the voltage controlling device and causing cost increase.

There arises another problem in that, although the voltage controllingdevice is configured such that a control voltage is adjustable asdesired, a circuit for determining an external input signal in thevoltage controlling device is required, and therefore the configurationof the voltage controlling device becomes very complicated and stillcauses cost increase.

The present invention, which has been made to solve the above-mentionedproblems, has an object to provide a system for controlling a vehiclulargenerator which requires no exclusive input terminal for an externalsignal, thereby simplifying system configuration and achieving costreduction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing a system for controlling avehiclular generator according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a specific example of an externalcontrol unit according to Embodiment 1 of the present invention.

FIG. 3 is a diagram for explaining an example of duty-voltage conversionin an external control unit according to Embodiment 1 of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, Embodiment 1 of the present invention will be describedwith reference to the drawings.

In FIG. 1, a generator (alternator) 10 is composed of a voltagecontrolling device 1 and a voltage generating section 2.

The voltage controlling device 1 includes a generator controller drivingterminal IG and an external voltage sensing terminal S. An outputterminal of a battery 4 is connected to the generator controller drivingterminal IG through a key switch 3 and an output terminal of the battery4 is connected to the external voltage sensing terminal S through anexternal control unit 5.

The voltage controlling device 1 includes a power transistor 101constituting a control output circuit, a diode connected in inversepolarity to a collector terminal of the power transistor 101, atransistor 103 connected to a base terminal of the power transistor 101,a resistor 104 connected to a collector terminal of the transistor 103,a comparator 105 connected to a base terminal of the transistor 103,voltage dividing resistors 106 and 107 connected to a non-inversioninput terminal (+) of the comparator 105, and a resistor 108 and a Zenerdiode 109 for generating a constant-voltage power source V1.

One ends of the resistors 104 and 108 are connected to the generatorcontroller driving terminal IG and one end of the resistor 106 isconnected to the external voltage sensing terminal S. Further, areference voltage Vref is applied to an inversion input terminal (−) ofthe comparator 105.

The voltage generating section 2 in the generator 10 includes a fieldcoil 201 on a rotor side connected between the output terminal of thebattery 4 and the collector terminal of the power transistor 101,three-phase windings 202 on a stator side, and rectifying circuits 203for rectifying all waves of respective generator output voltages fromthe three-phase windings 202. Output terminals of the rectifyingcircuits 203 are connected to the output terminal of the battery 4.

In FIG. 1, the voltage controlling device is different from aconventional device exclusively in that the external control unit 5 forinducing a voltage drop between the external voltage sensing terminal Sof the voltage controlling device 1 and the battery 4.

Hereinafter, a basic operation of the voltage controlling device 1 shownin FIG. 1 will be described.

When the key switch 3 is closed (turned on) upon vehicle starting, abase current is supplied from the battery 4 through the resistor 104 tothe power transistor 101, so the power transistor 101 is madeconductive, resulting in the field current flowing through the fieldcoil 201 to thereby enable the generator 10 to generate electric power.

In addition, a battery voltage VB is applied to the cathode of the Zenerdiode 109 from the battery 4 through the resistor 108, and thus aconstant-voltage power source V1 is generated.

Further, a reference voltage Vref with respect to the comparator 105 isgenerated based on the constant-voltage power source V1.

When the generator 10 starts to generate electric power due to startingof the engine, the voltage controlling device 1 detects an input voltage(corresponding to the battery voltage VB) from the external voltagesensing terminal S and inputs it to the comparator 105 through thevoltage dividing resistors 106 and 107.

When the inputted voltage thus detected becomes higher than thepredetermined reference voltage Vref, the comparator 105 raises theoutput voltage to a high-level.

This causes the transistor 103 to be made conductive to cut off thepower transistor 101, whereby the field current flowing into the fieldcoil 201 is reduced to lower the generator output voltage from thegenerator 10.

On the other hand, when the detected voltage becomes lower than thereference voltage Vref due to lowering of the battery voltage VB, thecomparator 105 decreases the output voltage to a low-level.

This causes the transistor 103 to be cut off and the power transistor101 to be made conductive, whereby the field current is increased toraise the generator output voltage of the generator 10.

As described above, the generator output voltage of the generator 10 isadjusted to be an appropriate voltage in accordance with the referencevoltage Vref by the voltage controlling device 1.

Next, with reference to FIGS. 1 and 2, the external control unit 5 willbe described.

FIG. 2 is a block diagram showing a specific example of the externalcontrol unit 5.

In FIG. 2, the external control unit 5 includes an input terminal 5 aconnected to the battery 4, an output terminal 5 b connected to theexternal voltage sensing terminal S, a ground terminal 5 c grounded, anoperation state detecting section 501 for detecting an operation stateof a vehicle, a duty signal generating section 502 for generating a dutysignal set variable in accordance with the operation state, aduty-voltage conversion circuit 503 for converting the duty signal to apredetermined voltage, a current mirror circuit 50 connected to a line Lbetween the input terminal 5 a and the output terminal 5 b, and aresistor 507 inserted in the line L.

The current mirror circuit 50 is composed of a resistor 504 to which apredetermined voltage V2 outputted from the duty-voltage conversioncircuit 503 is applied and a pair of transistors 505 and 506 whoseemitter terminals are grounded.

One transistor, the transistor 505 is inserted between the resistor 504and the ground terminal 5 c and the other transistor, the transistor 506is inserted between the line L and the ground terminal 5 c; respectivebase terminals of the transistors 505 and 506 are coupled with eachother and connected to the resistor 504.

With the above configuration, the current mirror circuit 50 isconfigured so that a constant-current based on the predetermined voltageV2 may be absorbed from the line L. In addition, the constant-currentabsorbed by the current mirror circuit 50 is set to value proportionateto the duty signal and a voltage drop caused by the constant-current isproportionate to an amplitude of the constant-current.

In the external control unit 5, the vehicle state detecting circuit 501detects an operation state of the engine based on information such as avehicle speed, a cooling water temperature of the engine, and anelectric load.

The duty signal outputted from the duty signal generating circuit 502corresponding to the operation state is converted to the predeterminedvoltage V2 by the duty-voltage conversion circuit 503.

Subsequently, the constant-current proportionate to the predeterminedvoltage V2 is absorbed from the line L (the output terminal of thebattery 4 through the resistor 507) by the current mirror circuit 50 inthe external control unit 5.

At this time, a voltage drop corresponding to a voltage deviation ΔV iscaused between the input terminal 5 a and the output terminal 5 b of theexternal control unit 5 due to a current consumed by the resistor 507 inthe line L.

This voltage drop allows adjustment on the battery voltage VB to behigher by the voltage deviation ΔV than the voltage at the externalvoltage sensing terminal S as the adjustment voltage of the voltagecontrolling device 1.

FIG. 3 is a diagram showing a specific example of the conversionoperation by the duty-voltage conversion circuit 503.

In FIG. 3, the horizontal axis represents the duty signal (0%- 100%) inthe external control unit 5 and the vertical axis represents thepredetermined voltage V2 and battery voltage VB (voltage deviation ΔV)after conversion, and relations therebetween are shown.

Needless to say, the set value of each voltage, the slope of thecharacteristic line, etc. shown in FIG. 3 can be changed easily andarbitrarily by a set specification of the current mirror circuit 50, aset resistance value of the resistor 507, or the like.

As described above, in the system for controlling a vehiclular generatoraccording to the present invention, the external control unit 5 causinga voltage drop is inserted between the external voltage sensing terminalS and the battery 4, whereby an exclusive input terminal for an externalsignal can be omitted, thereby simplifying the system configuration andachieving cost reduction.

In addition, at this time, no complicated circuit is additionallyrequired in the voltage controlling device 1 of the generator 10 for avehicle, thereby enabling the system to combine with the voltagecontrolling device 1 similar to the conventional one, whereby a systemfor controlling electric generation, which is capable of highly precisecontrol can be provided at low costs with ease.

1. A system for controlling a vehicular generator, comprising: a voltagecontrolling device for adjusting a generator output voltage of agenerator connected to an in-vehicle battery to a predetermined voltage,the voltage controlling device including an external voltage sensingterminal for detecting an external voltage of the generator, and thegenerator output voltage being adjusted through on/off control of afield current of the generator in accordance with the external voltage,characterized in that an external control unit is inserted between theexternal voltage sensing terminal and the battery to generate a voltagedrop.
 2. The system for controlling a vehicular generator according toclaim 1, characterized in that: the external control unit includes anoperation state detecting section for detecting a vehicle operationstate; and the voltage drop is variably set in accordance with theoperation state.
 3. The system for controlling a vehicular generatoraccording to claim 2, characterized in that the external control unitincludes: an input terminal connected to the battery; an output terminalconnected to the external voltage sensing terminal; a duty signalgenerating section for generating a duty signal; a duty-voltageconversion circuit for converting the duty signal to a predeterminedvoltage; and a current mirror circuit for absorbing a constant-currentbased on the predetermined voltage from a line between the inputterminal and the output terminal.
 4. The system for controlling avehicular generator according to claim 3, characterized in that the dutysignal generating section variably sets the duty signal in accordancewith the operation state.
 5. The system for controlling a vehiculargenerator according to claim 3, characterized in that: theconstant-current is set to a value proportionate to the duty signal; andthe voltage drop corresponds to the constant-current.
 6. The system forcontrolling a vehicular generator according to claim 4, characterized inthat: the constant-current is set to a value proportionate to the dutysignal; and the voltage drop corresponds to the constant-current.